Method of producing a composite liquid



United States Patent METHOD OF PRODUCING A COMPOSI'IE'LIQUID BITUMINOUSBINDER John F. Beaver, Piqua, Ohio No Drawing. Original No. 2,602,774,dated July 8, 1952, Serial No. 26,475, May 11, 1948. Application forreissue July 12, 1955, Serial No. 521,655

3 Claims. (Cl. con- 52 This application is a continuation-in-part of mycopending application, Serial No. 571,543, filed January 5, 1945, nowabandoned.

This invention deals with bright copper plating, and in particular withbright copper plating by electrolysis from an acid bath.

It is an object of this invention to provide a bright copper deposit byelectrolysis froman acid bath which yields smooth and very uniformdeposits.

It is an object of this invention to provide a bright copper deposit byelectrolysis from an acid bath which yields a coating of an exceedinglyhigh luster so that butting is not necessary.

It is another object of this invention to provide a a bright copperdeposit by electrolysis of an acid bath with which operationcan besatisfactorilycontinued over a long period of time without noticeabledeterioration of the bath or impairment of the coating.

It is still another object of this invention to provide a bright copperdeposit by electrolysis. of anacid bath with which an electric currentof high density maybe used.

It is still another object of this invention to provide a bright copperdeposit by electrolysis of an acid bath which does not require frequentrenewal of the electrode and discarding of the bath used.

It is still another object of this invention to provide a bright copperdeposit by electrolysis using an acid bath which does not become turbidafter some time so that a filtering step does not have to be insertedfrom time to time.

It is still another object of this invention to provide a bright copperdeposit by electrolysis using an acid bath which has a highly increasedtolerance for impurities.

It has been found by the applicant during comprehensive research workthat, while electrolytes based on a mixture of copper, sulphate andsulfuric acid operate satisfactorily in the beginning, the depositsbecome less and less uniform as the operation continues. This phenomenonwas even noticed although the proportions of the ingredients of the bathwere constantly kept at the same level. As a consequence of thedisadvantage just described the electrolyte had to be discarded atfrequent intervals and replaced by a new one.

After a great many experiments it was discovered that the change of thecontent of chloride anion is responsible for such unsatisfactoryoperation.

After this discovery it was then found out that the electrolytes whenfirst used in the beginning had a very low content of chloride anionswhich were present in the form of a contamination, but that thischloride content became gradually depleted. This was when the operationstarted to become unsatisfactory.

Further studies of the problem revealed that if the chloride anioncontent of the electrolyte is controlled so as to bring it within arange of from 0.001 to 0.015 gram "ice per liter of electrolyte allthese disadvantages are overcome. A bath thus composed yields depositsof the desired properties for a very considerable period of time.

The essence of the invention thus consists in providing an electrolytefor acid copper plating in which the chloride anion content ranges from0.001 to 0.015 gram per liter.

As has been mentioned above the predominant ingredients of the bathpreferred for the electrolysis are copper sulphate and sulfuric acid.

It is advantageous to add a brightening agent to the electrolyte;derivatives of thiourea have been found especially suitable for thispurpose, and in particular acetyl thiourea has yielded excellentresults.

It is also advantageous, though optional, to add an agent which permitsthe use of an electric current of high density. Dextrin, molasses andcaramel are excellent for this purpose.

Sometimes it is also desirable to add a wetting agent; sodium laurylsulfate and sodium octyl sulfate are preferred therefor.

The invention thus consists in an electrolytic bath which contains:

to 275 gr./l. copper sulfate 20 to 100 gr./l. sulfuric acid 0.001 to0.015 g'r./l. chloride anion 0 to 1.0 gr./l. caramel dextrin and/ormolasses 0.005 to 0.05 gr./l. of acetyl thiourea The articles to beplated are advantageously subjected to a preliminary treatment prior tothe coating proper. For this purpose they are cleaned with analkalinecleaner, dipped into acid in order to remove anyrush-neutralized and then rinsed in water. It is also preferable tofirst apply a thin copper coating from a cyanide bath. Such abath maycontain from 3 to v5 ounces of copper metal per gallon, 1 to 3 ounces offree sodium cyanide and from 2 to 8 ounces of sodium carbonate. Platingwith this bath for from 3 to 4 minutes is sufficient. After this flashplating the article is washed to remove the cyanide.

It is furthermore advantageous to agitate the electrolyte duringelectrolysis. This may be carried out either by moving the cathode or bystirring the electrolyte, the latter being preferred. In particular ithas been found satisfactory to effect stirring by blowing air throughthe bath. If stirring is carried out this way, however, it is advisableto restrict the quantity of the wetting agent to a minimum or omit itentirely, because otherwise excessive foaming takes place which impairsthe operation.

The temperature of the bath is preferably maintained at between and 100F. The electric current should have a voltage of from 2.5 to 6 volts anda density of from 40 to 200 amps. per square foot.

In the following, two examples are given for the pur pose ofillustrating my invention:

EXAMPLE I An electrolyte was used having the following composition: 250gr./l. CuSO4..5I-I2O 60 gr./l. sulfuric acid 0.005 gr./l. chloride anion0.10 gr./1. dextrin 0.015 gr./l. acetyl thiourea 0.02 gr./ 1. sodiumoctyl sulfate The bath had a temperature of F. Agitation was carried outby blowing air through the bath. The electric current had a density ofamps. per square foot and a voltage of 4.5 volts.

The coating obtained in this instance was extremely smooth and uniformand had a high luster. The bath did not show any turbidity even after ause of several weeks.

The tolerance for impurities for a bath of this invention isconsiderably increased in particular for iron, zinc, chromium andnickel. For instance, without the presence of chloride anions, harmfuland impairs the operation. With a chloride anion content as set forth inthis specification several grams per liter may be present in theelectrolyte and the operation will be satisfactory.

EXAMPLE II 200 gr./l. copper sulfate 50 gr./l. sulfuric acid 0.005gr./l. chloride anion 0.10 gr./l. caramel and/ or molasses .03 gr./l.acetyl thiourea 0.10 gr./l. sodium lauryl sulfate The process with thiselectrolyte was carried out under the same conditions as were used inconnection with Example I with the exception that agitation of theelectrolyte was eifecte'd by moving the cathode instead of introducingair. The same favorable results were obtained.

It will be understood that while there have been described hereincertain specific embodiments of my invention, it is not intended therebyto have it limited to the details given in view of the fact that thisinvention is susceptible to various modifications and changes that comewithin the spirit of the disclosure and the scope of the appendedclaims.

I claim:

1. In a method of electrolytically depositing copper from a coppersulfate-sulphuric acid bath containing acetyl thiourea in an amount offrom about 0.005 to 0.05 gm./1. and chloride anion in an amount of fromabout 0.001 to 0.015 gm./l., the step of maintaining the chloride anionconcentration at a constant value within the range of about 0.001 to0.015 gm./l. by addition of a chloride[.], and wherein the bath ismaintained at a current density of from 40 to 200 amperes per squarefoot.

an iron content of 0.25 gr./1. is'

2. In a method of electrolytically depositing copper from a coppersulfate-sulfuric acid bath containing a thiourea compound in an amountof from about 0.005 to 0.05 gm./l. and chloride anion in an amount offrom about 0.001 to 0.015 gm./l., the step of maintaining the chlorideanion concentration at a constant value within the range of "about 0.001to 0.015 gm./l. by addition of a chloride[.], and wherein the electriccurrent density is from to 200 amperes per square foot, with voltage of2.5 to 6.0.

3. In a method of electrolytically depositing copper from a coppersulfate-sulphuric acid bath containing a thiourea compound in an amount09 from about 0.005 to 0.05 gnu/l. and chloride anion in an amount offrom about 0.001 to 0.015 gm./ L, the step of maintaining the chlorideanion concentration at a constant value within the range of about 0.001to 0.015 gm./l. by addition of a chloride and wherein the bath ismaintained at between about and F. and the electric current density isfrom 40 to 200 amperes per square foot with a voltage of 2.5 to 6.0.

References Cited in the file of this patent or the original patentUNITED STATES PATENTS Buswell: Chemistry 1929, pp. 74-76.

Operating Manual, Daybrite Acid Copper Process, pp. 2-3.

of Water and Sewage Treatment,

